precedent

There are no precedents for these events. [=nothing like these events has ever happened before]这种事还从未有过先例。

There isn't any precedent for these events. = These events are without precedent.这种事还从未有过先例。

The judge's ruling was based on a precedent established by an earlier decision.法官的裁决是基于一个早前确定的判例。

He says that the government will set/establish a dangerous precedent if it refuses to allow the protesters to hold a rally.他说政府如果不允许抗议者举行集会，它将确立一个危险的判例。

The judge's ruling was based/founded on legal precedent.法官的裁决是基于具有法律效力的判例做出的。

The voters broke (with) precedent [=they did something that had not been done before] when they elected a woman to the position.选民们打破惯例，选了一位女性任职。